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ADS1198: ADS1198 NOISE issue

Bhairu Patil1
Intellectual 570 points
Part Number: ADS1198

Dear TI Team,

 We are using ADS1198 in our design. Recently, we are seeing the Noise issue in our devices. and the system is failing to detect a lead off during this scenario, due to which noisy ECG signal is being processed and the wrong arrhythmia's are getting detected.

Please, find the attachment, and provide your inputs at the earliest on the following.

  • What is the reason for these noise?,and how to fix it?.
  • why Lead off is not getting detected?.
    • The following are the register settings used for Lead-off detection.
      • CONFIG3           =  0XCC
      • LOFF                 =  0X0F
      • LOFF_SENSP = 0XFF
      • LOFF_SENSN = 0X04

Thanks and Regards,

Bhairu

  • 0
    TI__Mastermind 38745 points

    Hello Bhairu,

    Are you certain the noise is due to a high impedance connection to the patient? How do you know that the impedance is high enough such that lead-off detection ought to detect it?

    If the impedance is high, then the noise could be coming from the  environment. If the impedance is low, environment noise is sinked into the RL amplifier so it's magnitude is low. If the impedance is high, the noise will be large.

    We have spoken in the past at length about the operation of the lead-off detection circuit (here and here), so I know you are familiar with the details of the implementation. As you know from our past discussions, lead-off detection takes place when the voltage at the inputs is outside of the comparator thresholds like it is shown in Figure 46 in the datasheet. To test the voltage at the inputs, you can probe them with respect to AVSS. What are the voltages when you probe it?

    Brian